STARTing down the long road

Let us rejoice, but with suitable restraint, over what is still the main news of the week in world affairs, even though it has been obscured by the Falkland Islands affair.

Messrs. Ronald Reagan of Washington and Leonid Brezhnev of Moscow have reached agreement that they want to, and in all probability will soon, begin to talk with each other about possible ways of reducing their respective nuclear arsenals.

But let us not in our rejoicing over this desirable prospect forget that any agreement is not only months, but possibly even years down the road. Agreement is far away because the decision that must be made before there can be agreement might seriously affect the relative security of either of the two superpowers at some as yet unforeseeable point in the future. Each will be supercautious about concessions.

And in the case of each of the two superpowers there are critics at home ready to pounce on any concession that just might seem to be unbalanced by an equivalent concession from the other. Add that in both Moscow and Washington there are equally impassioned ideologues who oppose the very idea of business being done with the other.

The result is that Messrs. Reagan and Brezhnev are cast in the roles of classic oriental rug traders getting ready to bargain over the most valuable items in their respective collections. This can be the negotiation of the century.

The outcome could range all the way from nothing to a new and less dangerous relationship between the superpowers. The chances are for something modest in between, probably nearer the nothing end of the scale than the major-accomplishment end of the scale.

As in any negotiation where the stakes are high, the opening positions are ritualistic. They do not deserve the attention paid to them in the current news. Mr. Reagan opens the bidding by talking about a one-third drop in existing arsenals, which he knows perfectly well Mr. Brezhnev cannot accept. And Mr. Brezhnev opens for his side by claiming that the United States is seeking an advantage--which of course Mr. Reagan would be delighted to get, if he could.

Carefully concealed in these opening maneuvers are the final fall-back positions of the two sides. Such positions exist. Years of thinking and staff work have been done on both sides. Each knows the maximum it would hope to get out of the negotiation and the minimum it must get if there is to be an agreement.

But these final positions must be concealed both because that is the nature of the bargaining process and because disclosure now would immediately plunge the process into the arena of domestic politics.

Take as a theoretical example what would happen if it became known that the US final fall-back position included abandonment of the new US Trident submarine program. (I have no reason whatever to think that it does.) Instantly, the four senators from Connecticut and Rhode Island would be beating their way into the Oval Office, probably with the rest of the New England congressional delegation behind them. The potential loss of employment for New England would be horrifying to any politician, particularly for those from Connecticut and Rhode Island, where the Tridents are assembled.

The political process is similar, although concealed, in the Soviet Union. Mr. Brezhnev may already have had to promise the commissar from some oblast in the Urals that under no circumstance will he abandon a weapon that may be built in a factory in his town.

Job protection is a heavy factor in any negotiation over arms control or limitation or reduction. This is only one reason why it is usually easier to put a lid on existing weapons programs than to eliminate or reduce the supply of any particular weapon. A reduction in the number means a slowdown or a closing down of some assembly line, hence some unemployment.

There are also profits for stockholders in the US, and managerial positions for party leaders in the Soviet Union to be considered. Economics and domestic politics are involved deeply in the process of trying to reduce the number, the range, and the damage characteristics of a weapon.

However, the essential fact remains that Mr. Reagan is doing what was inconceivable when he entered the White House 16 months ago. At that time it was standard doctrine at the White House that the US would negotiate with the Soviets only if they first withdrew their forces from Afghanistan and refrained from doing anything unpleasant about Poland. That is the doctrine of ''linkage.''

Soviet troops are still in Afghanistan and martial law still prevails in Poland. Under the doctrine of ''linkage'' the US would continue to refuse to do any business of any kind with Mr. Brezhnev. But, as have other presidents before him, Mr. Reagan has come round to recognize that there is a distinction to be drawn between the things the Soviets do to increase their range of influence in the world and the weapons that might come into use in a confrontation.

There may well be confrontations in the months ahead between Moscow and Washington over some action that either might take in the interests of what it deems to be its security. For example, it is not inconceivable that the US would send its troops into either Nicaragua or Cuba. There are no immediate plans, but certainly a number of high--placed Reagan administration officials came to Washington wanting, and expecting, to do that.

It is equally conceivable that the Soviets would send their own troops into some rebellious satellite or move into Iran.

Such actions could lead to a serious confrontation and a difficult crisis. But what kinds of weapons would come into play as factors in the confrontation? Moscow and Washington are unlikely to be able to rule out possible confrontations over some issue that one or the other might consider to involve a vital national interest.

But they just might be able to agree at the end of the process that opened up this past week to reduce the types and kinds of weapons that would be in the background of such a confrontation. They might even someday be able to delete nuclear weapons from the pattern. Any move in such a direction would be a gain for the human race. The past week has seen one small step taken down that road.